U.S. patent number 11,124,314 [Application Number 15/951,855] was granted by the patent office on 2021-09-21 for systems and methods for transferring electric power to an aircraft during flight.
This patent grant is currently assigned to The Boeing Company. The grantee listed for this patent is The Boeing Company. Invention is credited to Brian J. Tillotson.
United States Patent |
11,124,314 |
Tillotson |
September 21, 2021 |
Systems and methods for transferring electric power to an aircraft
during flight
Abstract
Systems and methods for transferring electric power to an
aircraft during flight. Power transfer to the receiver aircraft is
effected by means of a donor aircraft using a wired electrical
connection. The method for transferring electric power includes:
establishing an electrical connection between a receiver aircraft
and a donor aircraft during flight; and transferring electric power
from the donor aircraft to the receiver aircraft via the electrical
connection. In one embodiment, electric power is transferred by way
of a power cable deployed by the donor aircraft, a drogue attached
to a trailing end of the power cable, and a probe mounted to the
fuselage of the receiver aircraft, The probe and drogue are
configured to form an electrical connection when fully engaged.
Inventors: |
Tillotson; Brian J. (Kent,
WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
The Boeing Company |
Chicago |
IL |
US |
|
|
Assignee: |
The Boeing Company (Chicago,
IL)
|
Family
ID: |
68160969 |
Appl.
No.: |
15/951,855 |
Filed: |
April 12, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190315479 A1 |
Oct 17, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64D
41/00 (20130101); G06T 7/97 (20170101); G01S
5/0072 (20130101); H02J 7/342 (20200101); G06T
7/73 (20170101); B60L 53/57 (20190201); G01S
5/0231 (20130101); B60L 53/37 (20190201); B60L
53/16 (20190201); B60L 53/36 (20190201); H02G
11/02 (20130101); H02J 7/0042 (20130101); Y02T
10/70 (20130101); B64C 2201/066 (20130101); B64D
2221/00 (20130101); Y02T 90/14 (20130101); Y02T
10/7072 (20130101); B64D 39/00 (20130101); G01S
19/42 (20130101); B60L 2260/32 (20130101); B60L
2200/10 (20130101); H02J 2310/44 (20200101); B64C
39/024 (20130101); Y02T 90/12 (20130101) |
Current International
Class: |
B64D
41/00 (20060101); G01S 5/02 (20100101); H02G
11/02 (20060101); G06T 7/00 (20170101); H02J
7/34 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Xavier; Valentina
Attorney, Agent or Firm: Ostrager Chong Flaherty &
Broitman P.C.
Claims
The invention claimed is:
1. A system for transferring electric power, comprising: a receiver
aircraft comprising a first fuselage and a first coupling device
externally mounted to the first fuselage, wherein the first
coupling device comprises first and second electrical contacts and
first and second electrical conductors respectively connected to
the first and second electrical contacts; and a donor aircraft
comprising a second fuselage and a second coupling device
positioned aft of the second fuselage, wherein the second coupling
device comprises third and fourth electrical contacts and third and
fourth electrical conductors respectively connected to the third
and fourth electrical contacts, wherein the first and second
electrical contacts are respectively in contact with the third and
fourth electrical contacts when the first and second coupling
devices are coupled together; wherein one of the first and second
coupling devices has an annular groove and the other of the first
and second coupling devices comprises a piston that fits into the
annular groove for locking the first and second coupling devices
together, a crank connected to the piston, and a motor having an
output shaft connected to the crank; and wherein the piston is
displaced radially inward into the annular groove when the motor
drives rotation of the crank.
2. The system as recited in claim 1, wherein the second coupling
device comprises first and second springs for urging the third and
fourth electrical contacts into contact with the first and second
electrical contacts.
3. The system as recited in claim 1, wherein the first and second
electrical contacts are circular bands made of electrically
conductive material.
4. The system as recited in claim 1, wherein the donor aircraft
further comprises a power supply and the receiver aircraft further
comprises a battery and a battery charger configured to recharge
the battery with electric power supplied by the power supply
onboard the donor aircraft when the first and second coupling
devices are coupled together.
5. The system as recited in claim 1, wherein: the donor aircraft
further comprises a beacon for transmitting a beacon signal and a
first computer system configured to encode digital information in
the beacon signal; and the receiver aircraft further comprises a
beacon sensor for sensing the beacon signal and a second computer
system configured to decode the digital information in the beacon
signal.
6. The system as recited in claim 5, wherein the first coupling
device further comprises a camera and the second computer system is
further configured to receive image data representing an image from
the camera and then use an image recognition algorithm to extract
feature descriptors and match the extracted features to recognize
the image.
7. The system as recited in claim 1, wherein the first coupling
device is a probe and the second coupling device is a drogue.
8. The system as recited in claim 7, wherein: the receiver aircraft
further comprises a probe support pipe attached to the first
fuselage; the probe is attached to one end of the probe support
pipe; and the first and second electrical conductors extend from
the probe to another end of the probe support pipe.
9. The system as recited in claim 8, wherein: the donor aircraft
further comprises a power cable extending rearward of the second
fuselage; the drogue is attached to one end of the power cable; and
the third and fourth electrical conductors extend from the drogue
to another end of the power cable.
10. The system as recited in claim 9, wherein the donor aircraft
further comprises a power supply and the receiver aircraft
comprises a battery charger that receives electric power from the
power supply onboard the donor aircraft via the first through
fourth electrical conductors when the first and second electrical
contacts of the probe are respectively in contact with the third
and fourth electrical contacts of the drogue.
11. A system for transferring electric power, comprising: a
receiver aircraft comprising a first fuselage and a first coupling
device externally mounted to the first fuselage, wherein the first
coupling device comprises first and second electrical contacts and
first and second electrical conductors respectively connected to
the first and second electrical contacts; and a donor aircraft
comprising a second fuselage and a second coupling device
positioned aft of the second fuselage, wherein the second coupling
device comprises third and fourth electrical contacts and third and
fourth electrical conductors respectively connected to the third
and fourth electrical contacts, wherein the first and second
electrical contacts are respectively in contact with the third and
fourth electrical contacts when the first and second coupling
devices are coupled together; wherein the first coupling device
comprises a hook, a pivot axle having opposing ends affixed to the
hook, and a pivotable latch that is rotatably coupled to the pivot
axle and spring-loaded; and wherein the second coupling device
comprises a trapeze bar configured to fit between the hook and the
pivotable latch when the pivotable latch is in a closed
position.
12. The system as recited in claim 1, wherein the receiver aircraft
further comprises a battery charger and an electrical connection
between the battery charger and the electrical contacts in the
coupling device.
13. The system as recited in claim 12, wherein the first coupling
device comprises a probe and the electrical contacts comprise
circular bands made of electrically conductive material.
14. The system as recited in claim 1, wherein the donor aircraft
further comprises a cable spool rotatably coupled to the fuselage,
a power supply, and a power transfer unit configured to transfer
electric power from the power supply in a power transfer mode, a
power cable connected to the cable spool and electrically coupled
to the power transfer unit, the second coupling device comprises a
drogue attached to the power cable, the power cable comprises
electrical conductors, and the drogue comprises the first and
second electrical contacts which are electrically coupled to the
electrical conductors of the power cable.
15. The system as recited in claim 11, wherein the donor aircraft
further comprises a power supply, a power transfer unit configured
to transfer electric power from the power supply in a power
transfer mode, and electrical conductors electrically coupled to
the power transfer unit, wherein the trapeze bar comprises the
third and fourth electrical contacts which are electrically coupled
to the electrical conductors and disposed on an external surface of
the trapeze bar.
16. A system for transferring electric power during flight,
comprising: a receiver aircraft comprising a first fuselage, a
battery, a battery charger connected to the battery, a rectifier
connected to the battery charger, and a first coupling device
externally mounted to the first fuselage, wherein the first
coupling device comprises first and second electrical contacts and
first and second electrical conductors respectively connecting the
first and second electrical contacts to the rectifier; and a donor
aircraft comprising a second fuselage, a power supply, a power
cable connected to the power supply, and a second coupling device
external to and positioned aft of the second fuselage, wherein the
second coupling device comprises third and fourth electrical
contacts connected to the power supply via the power cable, wherein
the first and second electrical conductors are cups having profiles
that are truncated cones; wherein the third and fourth electrical
conductors are annular bands; and wherein the first and second
electrical contacts are respectively in contact with the third and
fourth electrical contacts.
17. The system as recited in claim 1, wherein: the first and second
electrical conductors are cups having profiles that are truncated
cones: and the third and fourth electrical conductors are annular
bands.
18. The system as recited in claim 11, wherein: the pivotable latch
comprises sidewalls connected to and projecting in parallel from
side edges of a cross wall; and a lower portion of the hook has two
mutually parallel slots formed therein for receiving the sidewalls
of the pivotable latch when the pivotable latch is pushed by the
trapeze bar from the closed position to an open position.
19. The system as recited in claim 18, wherein the hook comprises
upper and lower guides that are configured to guide the hook into
lateral alignment with the trapeze bar as the trapeze bar enters
the hook.
20. The system as recited in claim 19, further comprising a
spring-loaded contact support reed supported by one of the upper
and lower guides and comprising a flexible reed made of
electrically insulating material and having the first and second
electrical contacts made of electrically conductive material formed
into bar-shaped strips attached thereto.
21. The system as recited in claim 20, wherein the trapeze bar has
a central narrow section having a diameter less than a diameter of
adjacent sections of the trapeze bar on opposite sides of the
central narrow section, the third and fourth electrical contacts
being made of electrically conductive material formed into annular
bands attached to the central narrow section.
Description
BACKGROUND
This disclosure generally relates to the transfer of electric power
to an aircraft during flight. In particular, this disclosure
relates to systems and methods for transferring electric power to
an aircraft for the purpose of battery recharging.
In order to extend the flight range of certain fuel-consuming
aircraft, some aircraft have been designed with in-flight refueling
or air-to-air refueling capabilities. One type of refueling system
includes a hose and drogue system carried by a tanker aircraft and
a probe extending forward from a fuel-receiver aircraft that is
flying behind the tanker aircraft. The hose and drogue system
includes a refueling hose having a drogue disposed at one end. The
drogue in such systems is usually a funnel-shaped device attached
to the end of a refueling hose for connecting with the probe of the
aircraft to be refueled in flight. The refueling hose connects to a
hose drum unit that is mounted to the fuselage of the tanker
aircraft. When placed in an air stream, the drogue acts to draw the
hose out of the aircraft and stabilize the flight of the hose when
extended. When not in use, the refueling hose and drogue is reeled
completely into the hose drum unit. During operation, the refueling
tanker flies straight and level and extends the refueling hose and
drogue, which trails behind and below the refueling tanker under
normal aerodynamic forces.
Fuel-consuming aircraft (including piloted airplanes and unmanned
aerial vehicles) produce carbon dioxide and noise. To avoid carbon
dioxide emissions and reduce noise, it is known to employ
electrically propelled aircraft. However, the range and flight
duration of electrically propelled aircraft are heavily limited by
the energy density of batteries. To achieve the same range and
duration as a fuel-consuming aircraft, an electrically propelled
aircraft would need to carry very large batteries if the batteries
were only charged at the start of flight. A way to improve the
range and duration of electrically propelled aircraft is to
recharge the battery during flight, e.g., by transferring
electrical energy from another aircraft.
Accordingly, it would be advantageous to provide improved systems
and methods for transferring electric power to an aircraft during
flight.
SUMMARY
The subject matter disclosed in some detail below is directed to
systems and methods for transferring electric power from a leading
aircraft (hereinafter "donor aircraft") to a trailing aircraft
(hereinafter "receiver aircraft") during flight. Power transfer
from the donor aircraft to the receiver aircraft is effected by
means of a wired electrical connection that is established and
maintained as the aircraft fly at the same speed along parallel
flight paths or the same flight path. The receiver aircraft may be
a piloted airplane or an unmanned aerial vehicle. The propulsion
system of the receiver aircraft may include electric motors powered
by batteries or fuel-consuming engines. Similarly, the donor
aircraft may be a piloted airplane or an unmanned aerial vehicle.
The propulsion system of the donor aircraft may include electric
motors or fuel-consuming engines.
In accordance with some embodiments, the donor aircraft is equipped
with a power supply (e.g., an alternating- or direct-current power
supply)), a power cable electrically coupled to the power supply
and a drogue attached to the end of the power cable, while the
receiver aircraft is equipped with a battery recharging system and
a probe mounted to a probe support pipe (e.g., a spar, boom or
beam) that extends forward from the nose of the aircraft. The probe
and drogue are configured to engage each other in a manner that
establishes a wired electrical connection. The probe and probe
support pipe are configured to carry current from the drogue to the
battery recharging system. The battery recharging system includes a
battery charger which uses direct current to recharge the batteries
onboard the receiver aircraft.
Although various embodiments of systems and methods for
transferring electric power to an aircraft during flight are
described in some detail later herein, one or more of those
embodiments may be characterized by one or more of the following
aspects.
One aspect of the subject matter disclosed in detail below is a
system for transferring electric power, comprising: a receiver
aircraft comprising a first fuselage and a first coupling device
externally mounted to the first fuselage, wherein the first
coupling device comprises first and second electrical contacts and
first and second electrical conductors respectively connected to
the first and second electrical contacts; and a donor aircraft
comprising a second fuselage and a second coupling device
positioned aft of the second fuselage, wherein the second coupling
device comprises third and fourth electrical contacts and third and
fourth electrical conductors respectively connected to the third
and fourth electrical contacts. The first and second electrical
contacts are respectively in contact with the third and fourth
electrical contacts when the first and second coupling devices are
coupled together. The donor aircraft further comprises a power
supply and the receiver aircraft further comprises a battery and a
battery charger configured to recharge the battery with electric
power supplied by the power supply onboard the donor aircraft when
the first and second coupling devices are coupled together.
In accordance with some embodiments of the system described in the
preceding paragraph, the first coupling device is a probe and the
second coupling device is a drogue. In accordance with other
embodiments, the first coupling device is a hook and the second
coupling device is a trapeze bar.
Another aspect of the subject matter disclosed in detail below is a
method for transferring electric power comprising: establishing an
electrical connection between a receiver aircraft and a donor
aircraft during flight; and transferring electric power from the
donor aircraft to the receiver aircraft via the electrical
connection. In accordance with some embodiments, establishing an
electrical connection comprises: deploying a drogue by unwinding a
power cable wound on a power cable spool carried by the donor
aircraft; navigating the receiver aircraft to a position where a
probe mounted to the receiver aircraft is inserted into the drogue;
and clamping the probe to the drogue; whereas transferring electric
power comprises: transferring electric power from the donor
aircraft to the drogue via the power cable; transferring electric
power from the drogue to the probe via electrical contacts; and
transferring electric power from the probe to a battery charger
onboard the receiver aircraft.
A further aspect of the subject matter disclosed in detail below is
an aircraft comprising a fuselage, a coupling device externally
mounted to the fuselage and comprising electrical contacts, a
battery charger disposed inside the fuselage, and an electrical
connection between the battery charger and the electrical contacts
in the probe.
Yet another aspect of the subject matter disclosed in detail below
is an aircraft comprising a fuselage, a cable spool rotatably
coupled to the fuselage, a power supply, a power transfer unit
configured to transfer electric power from the power supply in a
power transfer mode, a power cable connected to the cable spool and
electrically coupled to the power transfer unit, and a drogue
attached to the power cable, wherein the power cable comprises
electrical conductors and the drogue comprises electrical contacts
which are electrically coupled to the electrical conductors of the
power cable.
A further aspect is an aircraft comprising a fuselage, a trapeze
bar disposed outside the fuselage, a power supply, a power transfer
unit configured to transfer electric power from the power supply in
a power transfer mode, and electrical conductors electrically
coupled to the power transfer unit, wherein the trapeze bar
comprises first and second electrical contacts which are
electrically coupled to the electrical conductors and disposed on
an external surface of the trapeze bar.
Other aspects of systems and methods for transferring electric
power to an aircraft during flight are disclosed below.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, functions and advantages discussed in the preceding
section may be achieved independently in various embodiments or may
be combined in yet other embodiments. Various embodiments will be
hereinafter described with reference to drawings for the purpose of
illustrating the above-described and other aspects. None of the
diagrams briefly described in this section are drawn to scale.
FIG. 1 is a diagram representing a view of a receiver aircraft
approaching a drogue which has been deployed behind a donor
aircraft in accordance with one embodiment of an aerial electric
power transfer system.
FIG. 2 is a diagram representing a view of a drogue and a probe in
a state of engagement that allows electric power to be transferred
from a donor aircraft to a receiver aircraft during flight.
FIG. 3 is a diagram representing a sectional view of half of a
drogue through an axis of symmetry in accordance with one
embodiment.
FIG. 4 is a diagram representing a sectional view of half of a
probe through an axis of symmetry in accordance with one
embodiment.
FIG. 5 is a diagram representing a sectional view of a
camera-equipped probe as it approaches a drogue of the type
depicted in FIG. 3.
FIG. 6 is a block diagram identifying some components of a typical
unmanned aerial vehicle.
FIG. 7 is a diagram identifying some components of a system for
recharging a battery onboard an aircraft during flight in
accordance with one embodiment.
FIG. 8 is a diagram identifying some components of a navigation
system onboard a receiver aircraft in accordance with one
embodiment.
FIG. 9 is a diagram identifying some components of an electric
power transfer system onboard a donor aircraft in accordance with
one embodiment.
FIG. 10 is a flowchart identifying steps of a method for aerial
electric power transfer in accordance with one embodiment.
FIG. 11 is a diagram representing a view of a hook and trapeze
mechanism for coupling one aircraft to another aircraft during
flight.
FIG. 12 is a diagram representing an end view of a trapeze bar
having a hook latched thereon in accordance with one
embodiment.
FIG. 13 is a diagram representing a top view of the lower portion
of the hook partly depicted in FIG. 12.
FIG. 14 is a diagram representing a view of a trapeze bar having a
narrow section equipped with electrical contacts for transferring
power to electrical contacts on the hook partly depicted in FIGS.
11 and 12.
FIG. 15 is a block diagram identifying some components of a system
for releasing a latch that is incorporated in the hook partly
depicted in FIGS. 11 and 12.
Reference will hereinafter be made to the drawings in which similar
elements in different drawings bear the same reference
numerals.
DETAILED DESCRIPTION
For the purpose of illustration, systems and methods for
transferring electric power to an aircraft during flight will now
be described in detail. However, not all features of an actual
implementation are described in this specification. A person
skilled in the art will appreciate that in the development of any
such embodiment, numerous implementation-specific decisions must be
made to achieve the developer's specific goals, such as compliance
with system-related and business-related constraints, which will
vary from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming, but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure.
FIG. 1 is a diagram representing a view of a receiver aircraft 4
approaching a drogue 12 which has been deployed behind a donor
aircraft 2 in accordance with one embodiment of an aerial electric
power transfer system. In the scenario depicted in FIG. 1, the
donor aircraft 2 and receiver aircraft 4 are flying along parallel
flight paths with the donor aircraft 2 leading the receiver
aircraft 4. Also the receiver aircraft 4 is flying at a slightly
greater speed than the speed of the donor aircraft 2. At the
juncture depicted in FIG. 1, the donor aircraft 2 has already
deployed a coupling device in the form of a drogue 12, which is
attached to the end of a power cable 10. The power cable 10 is
connected to a power supply (not shown in FIG. 1) disposed inside
the fuselage 3 of the donor aircraft 2. The power supply may be an
alternating-current (AC) power supply or a direct-current (DC)
power supply. The receiver aircraft 4 includes a fuselage 5, a
probe support pipe 6 attached to and extending forward of the
fuselage 5, and a coupling device in the form of a probe 8 attached
to the end of the probe support pipe 6. The probe 8 and the drogue
12 are configured to interengage to form a wired electrical
connection.
FIG. 2 is a diagram representing a view of drogue 12 and a probe 8
(not visible in FIG. 2 because the probe 8 is inside the drogue 12)
in a state of engagement that allows electric power to be
transferred from the donor aircraft 2 to the receiver aircraft 4
during flight. Electric power is transferred by means of one pair
of electrical conductors incorporated in the drogue 12 and power
cable 10 and another pair of electrical conductors incorporated in
the disposed in the probe 8 and probe support pipe 6. As will be
described later in some detail, the pair of electrical conductors
incorporated in the drogue 12 may be electrically coupled to the
electrical conductors incorporated in the probe 8 when the probe 8
is fully engaged with the drogue 12. In that state of full
engagement, one pair of electrical contacts (not shown in FIG. 2)
in probe 8 contact another pair of electrical contacts (not shown
in FIG. 2) in drogue 12, enabling electrical current to flow
between the electrical conductors in drogue 12 and the electrical
conductors in probe 8.
To achieve the state of full engagement depicted in FIG. 2, the
donor aircraft 2 and receiver aircraft 4 navigate into proximity
with each other at a rendezvous location. As will be described in
some detail below, this may be accomplished using respective global
positioning systems onboard the aircraft and also using a beaconing
system that includes a beacon onboard the donor aircraft 2 that
transmits beacon signals and a beacon sensor onboard the receiver
aircraft 4 that receives beacon signals.
When the donor aircraft 2 and receiver aircraft 4 are in proximity,
personnel onboard the donor aircraft 2 deploy the drogue 12. When
placed in an air stream, the drogue 12 acts to draw the power cable
10 out of the donor aircraft 2 and stabilize the flight of the
power cable 10 when extended. When not in use, the power cable 10
is wound on a cable spool (not shown in FIGS. 1 and 2, but see
cable spool 118 in FIG. 9) disposed inside the fuselage 3 of donor
aircraft 2 until drogue 12 is inside the fuselage 3. During
operation, the donor aircraft 2 flies straight and level and
extends the power cable 10 and drogue 12, which trails behind and
below the donor aircraft 2 under normal aerodynamic forces. After
drogue deployment, the receiver aircraft 4 is maneuvered by the
pilot or autopilot to bring the probe 8 into proper position for
entering and then engaging with the drogue 12. In accordance with
one proposed implementation, the receiver aircraft 4 maneuvers the
probe 8 towards the drogue 12 using a beacon sensor (not shown in
FIGS. 1 and 2, but see beacon sensor 48 in FIG. 8) configured to
allow precise maneuvers relative to beacon signals transmitted by a
beacon (not shown in FIGS. 1 and 2, but see beacon 106 in FIG. 9)
on the donor aircraft 2 and/or the drogue 12.
When the probe 8 is properly inserted into the drogue 12, pistons
(not shown in FIGS. 1 and 2, but see pistons 22a and 22b in FIG. 5)
incorporated in the drogue 12 are actuated to clamp the probe 8 in
place inside the drogue 12. This clamping operation may be
activated automatically by a computer system onboard the donor
aircraft 2 or manually by personnel onboard the donor aircraft 2.
In the clamped state, the electrical conductors in drogue 12 are
electrically coupled to the electrical conductors in probe 8. From
this moment on, the pilots or autopilots seek to fly the donor
aircraft 2 and receiver aircraft 4 at approximately equal speeds
and equal headings in order to maintain a constant spacing between
the donor aircraft 2 and receiver aircraft 4 during the power
transfer operation. While a constant spacing is being maintained,
the personnel onboard the donor aircraft 2 initiate the power
transfer operation, causing electric power to be transferred from a
power supply (not shown in FIGS. 1 and 2, but see power supply 94
in FIG. 9) onboard the donor aircraft 2 to a battery charger (not
shown in FIGS. 1 and 2, but see battery charger 18 in FIG. 7)
onboard the receiver aircraft 4 via the electrical connection
established by the coupled drogue 12 and probe 8. Upon completion
of the electric power transfer operation, the pistons 22a and 22b
are withdrawn, thereby releasing the probe 8 from the drogue 12.
The pilot or autopilot of the receiver aircraft 4 is then free to
maneuver the receiver aircraft 4 away from the donor aircraft 2 and
then fly to the next waypoint indicated in the flight plan for the
receiver aircraft 4.
The foregoing method 200 of aerial electric power transfer is
summarized in FIG. 10 as follows: (a) navigate the donor aircraft 2
and receiver aircraft 4 into proximity with each other (step 202);
(b) deploy the drogue 12 (step 204); (c) maneuver receiver aircraft
4 to bring the probe 8 into proper position for engaging the drogue
12 (step 206); (d) clamp the probe 8 in place inside the drogue 12
(step 208); (e) pilot the receiving and donor aircraft 2 at the
same speeds with the same headings in order to maintain a constant
spacing between the aircraft (step 210); (f) transfer electric
power from the donor aircraft 2 to the receiver aircraft (step
212); (g) monitor the amount of electric power transferred (step
214); (h) cease the transfer of electric power when a specified
threshold has been reached (step 216); (i) release the probe 8 from
the drogue 12 (step 218); (j) maneuver the receiver aircraft 4 away
from the donor aircraft 2 (step 220); and (k) then fly the receiver
aircraft 4 to the next waypoint indicated in the flight plan of the
receiver aircraft 4 (step 222).
Each of the donor aircraft 2 and receiver aircraft 4 may be
equipped with a respective communication and navigation system by
which the two aircraft may rendezvous in flight. As an example,
each communication and navigation system may include a respective
global positioning system (GPS) to measure the respective locations
of the aircraft and a radiofrequency (RF) datalink to enable each
aircraft to receive data representing the location of the other
aircraft.
In addition, the receiver aircraft 4 may be equipped with a sensing
and control system by which the receiver aircraft 4 may locate the
drogue 12 and maneuver close enough to enable the probe 8 to be
physically coupled to the drogue 12 without damage to either
aircraft or the power cable 10. As an example, the sensing and
control system may include a system of labels or beacons (e.g., on
the donor aircraft 2 and/or on the drogue 12), sensors on the
receiver aircraft 4 to detect those labels or beacons, and flight
controls to maneuver the receiver aircraft 4 into a position where
the probe 8 can engage the drogue 12. Examples of a beacon/sensor
combination include: (a) a differential GPS system; or (b) lights
on the donor aircraft 2, a camera on the receiver aircraft 4, and a
processor connected to the camera and to the flight control system.
Sensing and control may also include sensors or mechanisms that
sense when the probe 8 is in a proper position inside the drogue 12
and respond by activating an attachment mechanism, such as the
pistons 22a and 22b described above.
In addition, the receiver aircraft 4 may be equipped with a battery
charger 18 (see FIG. 7). The battery charger 18 may be configured
to change the voltage or regulate the duty cycle of the direct
current being supplied to the battery 86 during recharging.
Recharging continues until the receiver aircraft 4 has adequately
replenished its battery 86. Optionally, the battery recharging
system onboard the receiver aircraft 4 includes a battery
monitoring and control system (not shown in FIGS. 1 and 2, but see
BMCS 92 in FIG. 7). The battery monitoring and control system 92
regulates the flow of current into and out of various cells within
the battery 86 to avoid overcharging, overheating, cell imbalance,
and other issues.
The embodiment depicted in FIGS. 1 and 2 may employ attachment
mechanisms other than pistons. In a simple embodiment, the receiver
aircraft 4 has a probe 8 with at least two electrical conductors
along its length, at least two electrical contacts (not shown in
FIGS. 1 and 2, but see electrical contacts 36a and 36b in FIG. 4)
near a tip of the probe 8, and a surface suitable for gripping near
the tip of the probe 8. Either as part of the gripping action, or
as a later action, electrical contacts (not shown in FIGS. 1 and 2,
but see electrical contacts 28a and 28b in FIG. 3) in the drogue 12
move to form an electrical connection with the electrical contacts
36a and 36b on the probe 8. The gripping mechanism exerts enough
force to maintain the electrical connection despite minor
turbulence and control moves, but is weak enough to release if the
receiver aircraft 4 makes an intentional maneuver away from the
donor aircraft 2.
FIG. 3 is a diagram representing a sectional view of half of a
drogue 12 through an axis of symmetry in accordance with one
embodiment. FIG. 4 is a diagram representing a sectional view of
half of a probe 8 through an axis of symmetry in accordance with
the embodiment partly depicted in FIG. 3. The probe 8 and drogue 12
are configured to interengage and then interlock with each
other.
Referring to FIG. 3, the drogue 12 includes a drogue housing 14
shaped to provide aerodynamic stability when towed at the end of
the power cable 10. At the right side, the drogue housing 14 is
attached to the power cable 10 that extends from the donor aircraft
2. The drogue housing 14 includes an aerodynamic surface 14a, a
guide surface 14b (at an aft end of the drogue 12), a contact
surface 14c and a stop surface 14d. The drogue housing 14 may be
made of metal alloy or carbon fiber-reinforced plastic
material.
Referring to FIG. 4, the probe 8 includes a probe housing 16 that
is attached to the probe support pipe 6 that extends from the
receiver aircraft 4. The probe housing 16 includes a contact
surface 16a and a guide surface 16b. The probe housing 16 may be
made of metal alloy or carbon fiber-reinforced plastic
material.
If the probe 8 enters the drogue 12 with the axis of symmetry C2
(see FIG. 4) of the probe 8 out of alignment with the axis of
symmetry C1 (see FIG. 3) of the drogue 12, the guide surface 16b of
the probe housing 16 will abut and be guided radially inward by the
guide surface 14b of the drogue housing 14 until the axes of
symmetry C1 and C2 are generally collinear. As the probe 8
continues to travel further into the drogue 12, the guide surface
16b of the probe housing 16 will eventually abut and be stopped by
the stop surface 14d of the drogue housing 14. In this position, a
pair of motors 26 (only one of which are depicted in FIG. 3)
disposed inside drogue housing 14 are activated, which causes the
output shafts of the motors 26 to rotate. Although not shown in
FIG. 3, the motors 26 receive electric power and control signals
from the donor aircraft 2 by way of respective power/signal cords
incorporated in the power cable 10. The output shaft of each motor
26 is connected to a respective crank 24. Each crank 24 in turn is
connected to a respective one of the pistons 22a and 22b. As the
motor 26 drives rotation of the crank 24, the pistons 22a and 22b
(see FIG. 3) are displaced radially inward into an annular groove
40 formed in the outer periphery of the probe 8, thereby locking
the probe 8 in place. In this position, the probe 8 and rogue 12
become electrically coupled, which state is detected by a probe
contact sensor 112 (see FIG. 9).
Referring to FIG. 3, the power cable 10 includes two electrical
conductors 33a and 33b that run the entire length of the power
cable 10. Within the drogue 12, two electrical conductors 32a and
32b connect the power cable electrical conductors 33a and 33b to
two spring-mounted electrical contacts 28a and 28b respectively.
The electrical contacts 28a and 28b are urged radially inward by
respective springs 30a and 30b. When the probe 8 is fully seated
inside the drogue 12 and locked in place (as previously described),
the springs 30a and 30b press the electrical contacts 28a and 28b
against corresponding electrical contacts 36a and 36b respectively
disposed on the outer peripheral surface of the probe 8 (see FIG.
4) to deliver electric power to the battery charger 18 onboard the
receiver aircraft 4 via electrical conductors 40a and 40b. In
accordance with one proposed implementation, the electrical
contacts 28a and 28b (see FIG. 3) incorporated in the drogue 12 are
made of electrically conductive material formed into cups having
profiles which are truncated cones, whereas the electrical contacts
36a and 36b (see FIG. 4) incorporated in the probe 8 are made of
electrically conductive material formed into annular bands.
As seen in FIG. 3, a pair of electrical insulators 34a and 34b with
respective openings in which the spring-mounted electrical contacts
34a and 34b are seated keep the spring-mounted electrical contacts
28a and 28b from shorting to the drogue housing 14. As seen in FIG.
4, an annular electrical insulator 38 has a pair of annular grooves
in which the electrical contacts 36a and 36b are respectively
seated. The electrical contacts 36a and 36b are electrically
coupled to the battery charger 18 by way of respective electrical
conductors 40a and 40b which extend along the entire length of the
probe support pipe 6 (not shown in FIG. 4).
To summarize the embodiment depicted in FIGS. 3 and 4, when the
probe 8 partly depicted in FIG. 4 is fully inserted inside and
electrically conductively coupled with the drogue 12 partly
depicted in FIG. 3, electric power may be transferred from the
donor aircraft 2 to the receiver aircraft 4. More specifically,
electric power may be transferred from the power supply 94 onboard
the donor aircraft 2 to the battery charger 18 onboard the receiver
aircraft 4 by way of electrical conductors 33a and 33b in power
cable 10, electrical conductors 32a and 32b in drogue 12,
electrical contacts 28a and 28b in drogue 12, electrical contacts
36a and 36b in probe 8, and electrical conductors 40a and 40b in
probe 8 and probe support pipe 6.
Although not shown in FIG. 3, the drogue 12 may further include a
second pair of spring-loaded electrical contacts positioned
diametrally opposite to electrical contacts 28a and 28b and
electrically connected to electrical conductors 33a and 33b in
power cable 10 by a respective pair of electrical conductors
similar to electrical conductors 32a and 32b.
For example, FIG. 5 shows a spring-loaded electrical contact 28c
diametrally opposed to the spring-loaded electrical contact 28a.
The electrical contact 28c is pressed radially inward through an
opening in an electrical insulator 34c by a spring 30c. In this
case, the electrical contacts 28a and 28c inside the drogue 12 will
both contact the annular electrical contact 36a on probe 8 when the
probe 8 is fully seated in drogue 12. Similarly, electrical contact
28b and another electrical contact diametrally opposed to
electrical contact 28b will both contact the annular electrical
contact 36b on probe 8 when the probe 8 is fully seated in drogue
12. Electric power may be transferred concurrently through both
electrical connections.
In accordance with some embodiments, sensors are provided for
detecting when the probe 8 is fully seated in the drogue 12. For
example, this may be accomplished by sensing when electrical
connectivity has been established across the electrical contacts.
(Other embodiments may use optical or magnetic sensors, for
example.) When the sensors report to a computer system onboard the
donor aircraft 2 that the probe 8 is fully seated, that computer
system will output control signals that activate a clamping
mechanism. In accordance with the embodiment depicted in FIGS. 3
and 4, the clamping mechanism includes a pair of motors 26
mechanically coupled to a pair of pistons 22a and 22b (see FIG. 5),
which pistons 22a and 22b interlock with the annular groove 20
formed in the outer peripheral surface of the probe 8 (see FIG. 4)
when the pistons 22a and 22b are extended radially inward. The
control signals from the computer system are sent to a pair of
motor controllers (not shown in the drawings) which respectively
control operation of the motors 26. In an alternative embodiment,
the probe 8 may have a clamping mechanism to grasp the drogue 12.
Other embodiments may use a magnetic gripper or a spring-driven
piston with gripping force weak enough to release automatically
when the receiver aircraft 4 pulls away, etc.
FIG. 5 shows one example of a sensor to assist the probe's approach
and insertion into the drogue 12. In this example, the sensor is a
video camera 42 which is placed in a cavity 46 of the housing 17 of
a probe 8a. The field of view of the video camera 42 being directed
forward along the axis of symmetry of the probe 8a. A computer
system (not shown in FIG. 5, but see computer system 62 in FIGS. 6
and 8) or a human operator onboard the receiver aircraft 4 uses
imagery from the video camera 42 to adjust pitch and yaw as the
receiver aircraft 4 approaches the drogue 12. To accommodate aerial
electric power transfer at night, optionally the drogue 12 may be
provided with a known pattern of optical targets (e.g.,
retroreflective markers) and the probe 8a may be provided with
illuminators which emit light toward those optical targets. The
light returned from the optical targets produces spots in the
acquired images. The computer system 62 may be programmed with
object recognition software that is configured to detect the edges
of those spots and calculate the location (e.g., position and
orientation) of the drogue 12 relative to the probe 8a based on the
pixel locations of the spots in the acquired images. In alternative
embodiments, the computer system 62 may be programmed with object
recognition software that is configured to detect points on known
structural features of the drogue 12 and calculate the location
(e.g., position and orientation) of the drogue 12 relative to the
probe 8a based on the pixel locations of those points in the
acquired images
As seen in FIG. 5, the video camera 42 is connected to systems
onboard the receiver aircraft 4 by a power/signal cable 25 which is
passed through the probe support pipe 6. More specifically, the
video camera 42 may receive electric power from a battery onboard
the receiver aircraft 4 and activation signals from computer system
62. In addition, the power/signal cable 25 carries image data from
the video camera 42 to the computer system 62 for processing. The
electrical conductors 40a and 40b also pass through the probe
support pipe 6.
In accordance with the embodiment depicted in FIG. 5, the probe 8a
is usually surrounded by a retractable sheath 44 which protects the
probe 8a against damage. At the time when the donor aircraft 2
deploys the drogue 12, the retractable sheath 44 may be retracted
to expose the probe 8a. The exposed probe 8a may then be inserted
in the drogue 12.
In accordance with some embodiments, one or both aircraft may be
unmanned. In alternative embodiments, either or both aircraft may
be rotorcraft or lighter-than-air vehicles. In accordance with a
preferred embodiment, the receiver aircraft 4 is a battery-powered
unmanned aerial vehicle (UAV) having an electric motor-driven
propeller.
FIG. 6 shows the layout of major subsystems of a battery-powered
UAV 50 of a type which may employ the battery recharging system
disclosed herein. UAV 50 has a camera 42 in the front end thereof
and a motor 54 in the rear end thereof. The motor 54 drives
rotation of a propeller 56. All subsystems communicate with an
onboard computer system 62 via one or more data buses 64. The UAV
50 depicted in FIG. 6 has two antennas 66 and 68 respectively
mounted at the tips of wings 58 and 60. Each antenna connects to a
GPS receiver 70, a regular radio receiver (Rx) 72, and a radio
transmitter (Tx) 74. The UAV 50 further comprises actuators 76 and
flight instruments 78 which also communicate with computer system
62 via the one or more data buses 64. Although not shown in FIG. 6,
the UAV 50 further includes one or more batteries and a battery
charger.
The computer system 62 is configured for controlling the flight
path and maneuvering of the UAV 50. More specifically, the computer
system 62 may include a flight control computer (not shown in FIG.
6) that is configured to control actuators 76 as a function of GPS
data generated by the GPS receiver 70, control commands received by
the radio receiver 72, and flight plan information stored a
non-transitory tangible computer-readable storage medium. In
addition, the computer system 62 may include an image data
processor (not shown in FIG. 6) that is configured with object
recognition software for identifying and locating objects in the
field of view of the video camera 42.
In accordance with one embodiment, the UAV 50 depicted in FIG. 6 is
modified to include a probe 8a of the type depicted in FIG. 5, with
the video camera 42 embedded in the probe 8a. The probe 8a may then
be used to receive electric power from a donor aircraft 2 during
flight of the UAV 50. That electric power is then used to recharge
the batteries onboard the UAV 50.
FIG. 7 is a diagram identifying some components of a system for
recharging a battery 86 onboard a receiver aircraft 4 during flight
in accordance with one embodiment. This system includes: a power
supply 94 onboard a donor aircraft 2; a pair of electrical
conductors 33a and 33b incorporated in a power cable (not shown in
FIG. 7, but see power cable 10 in FIG. 1) that is deployed by the
donor aircraft 2; a pair of electrical contacts 28 incorporated in
a drogue 12 attached to a trailing end of the power cable 10; a
pair of electrical contacts 36 incorporated in a probe 8 mounted to
the fuselage 5 of a receiver aircraft 4 and in contact with
electrical contacts 28 when the probe 8 is fully seated in the
drogue 12; a pair of electrical conductors 40a and 40b incorporated
in the probe 8 and probe support pipe 6; and a pair of junctions 96
and 98 respectively disposed at the ends of electrical conductors
40a and 40b. This arrangement allows electric power from the power
supply 94 to be transferred to the junctions 96 and 98 by way of
electrical conductors 33a and 33b, electrical contacts 28 and 36,
and electrical conductors 40a and 40b.
In accordance with the proposed implementation partly depicted in
FIG. 7, the power supply 94 is an AC power supply. The junctions 96
and 98 onboard the receiver aircraft 4 are electrically coupled to
an electromagnet 80 which is incorporated in the probe 8 in a
position such that the electromagnet 80 will confront ferromagnetic
material incorporated in the drogue 12 (e.g., stop surface 14d seen
in FIG. 3 may be made of ferromagnetic material) when the probe 8
and drogue 12 are fully engaged. When the electromagnet 80 receives
alternating current from the power supply 94, the electromagnet
generates a magnetic force that attracts the ferromagnetic material
in the drogue 12, thereby securely holding the probe 8 stationary
inside the drogue 12. The electromagnet 80 may be substituted for
the above-described clamping mechanism for locking the probe 8 in
place when the electrical connection has been established. In an
alternative embodiment, the drogue 12 may include an electromagnet
that confronts ferromagnetic material incorporated in the probe
8.
In one proposed implementation, the electromagnet 80 is an
electro-permanent magnet. Electro-permanent magnets are solid-state
devices that have zero static power consumption (like permanent
magnets), but can be switched on and off like electromagnets. The
power only needs to be applied for a brief moment to toggle the
state to either on or off, which makes it more useful for
applications where overall power usage is preferably low. The use
of electro-permanent magnets also has the benefit that, if power is
lost, the coupling is still active.
The junctions 96 and 98 onboard the receiver aircraft 4 are also
electrically coupled to a rectifier 82 of a battery charging
system. The rectifier 82 converts alternating current from the
power supply 94 into direct current. The battery charging system
further includes: a smoothing capacitor 84 that is connected to the
rectifier 82; a battery charger 18 that is connected in parallel
with the smoothing capacitor 26; and a battery 86 having a positive
terminal 88 and a negative terminal 90 connected to the battery
charger 18. The battery charger 18 is configured to charge the
battery 86 using direct current from the rectifier 82. In
accordance with alternative embodiments, the power supply 94 may be
a DC power supply, in which case the rectifier 82 and smoothing
capacitor 84 would not be included.
In addition, the battery recharging system onboard the receiver
aircraft 4 includes a battery monitoring and control system 92
("BMCS 92" in FIG. 7). The battery monitoring and control system 92
regulates the flow of current into and out of various cells within
the battery 86 to avoid overcharging, overheating, cell imbalance,
and other issues. More specifically, the battery monitoring and
control system 92 includes a voltage regulator to avoid
overcharging the battery 86, a current limiter to ensure that
charging does not occur too rapidly, and temperature sensors which
indicate when charging should cease because the battery 86 is
overheating. After the battery 86 has been recharged, it can be
used to provide DC electric power to a load.
FIG. 8 is a diagram identifying some components of a navigation
system onboard a receiver aircraft 4 in accordance with one
embodiment. The navigation system is configured to control the
flight of the receiver aircraft 4 to bring the receiver aircraft 4
into proximity with the donor aircraft 2 and then maneuver the
receiver aircraft 4 to cause the probe 8 and drogue 12 to engage.
The navigation system includes a computer system 62, a video camera
42, a beacon sensor 48 and a GPS receiver 70. The computer system
62 may include a flight control computer that receives image data
from video camera 42, beacon signal data from beacon sensor 48, and
GPS data from the GPS receiver 70. The flight control computer may
be configured to send control signals to a multiplicity of
actuators 76 which control that positions of various control
surfaces 52 (e.g., ailerons, elevators, rudder, etc.) of the
receiver aircraft 4.
The GPS receiver 70 receives GPS signals for continuously
determining the global coordinate position of the receiver aircraft
4. Position signals representing the position coordinates of the
receiver aircraft 4 are broadcast by a transmitter (e.g., radio
transmitter 74 seen in FIG. 6) that is onboard the receiver
aircraft 4. In addition, position signals representing the position
coordinates of a rendezvous location are broadcast by the donor
aircraft 2 or a ground station (not shown) and received by a
receiver (e.g., radio receiver 72 seen in FIG. 6) that is onboard
the receiver aircraft 4. The pilot or autopilot of the receiver
aircraft 4 then uses this information to fly the receiver aircraft
4 toward the rendezvous location. Concurrently, the donor aircraft
2 also flies toward the rendezvous location. When the aircraft are
in proximity to each other, the drogue 12 is deployed from the
donor aircraft 2.
In accordance with one embodiment, the receiver aircraft 4 includes
complementary maneuver guidance systems: a beaconing system that
allows the computer system 62 onboard the receiver aircraft 4 to
trace the path of the donor aircraft 2 (or the path of the drogue
12 if the beacon 106 is mounted to the drogue 12) and object
recognition software that allows the computer system 62 to identify
and locate the drogue 12 by processing the images acquired by the
video camera 42. Any known object recognition technique may be
used, such as edge detection or feature extraction.
The donor aircraft 2 includes a beacon (see beacon 106 in FIG. 9)
that broadcasts beacon signals which are detected by the beacon
sensor 48 onboard the receiver aircraft 4. The beacon 106 is
preferably mounted on the tail of the donor aircraft 2; the beacon
sensor 48 is preferably mounted on the nose of the receiver
aircraft 4. The computer system 102 (see FIG. 9) onboard the donor
aircraft 2 is configured to encode digital information in the
beacon signal. The beacon signal is directed generally rearward by
the beacon 106. The beacon sensor 48 senses the beacon signal from
the beacon 106. The computer system 62 onboard the receiver
aircraft 4 is configured to decode the digital information in the
beacon signal.
In accordance with the embodiment shown in FIGS. 8 and 9, the
beacon 106 transmits data to beacon sensor 48, such as the
identity, position, speed and heading of the donor aircraft 2. The
beacon 106 may operate in the optical, infrared, or radiofrequency
(RF) spectrum, or a combination of these. A combination may ensure
that the beacon 106 and beacon sensor 48 can operate at night, in
adverse weather (including fog) and in the presence of smoke, dust
and other obscurants. In accordance with one proposed
implementation, the beacon 106 provides a narrow-band optical or RF
source and the beacon sensor 48 comprises a filter that filters the
received signals to that narrow band, making the beacon sensor 48
immune to optical or electromagnetic interference. The beacon 106
may be a laser that emits a conical beam encoded with
information.
As the receiving and donor aircraft communicate, the pilots or
autopilots control the respective speeds and headings of the two
aircraft until the receiver aircraft 4 reaches a position where the
probe 8 is behind and separated from the drogue 12. The pilot or
autopilot onboard the receiver aircraft 4 then maneuvers the
receiver aircraft 4 to bring the probe 8 into proper position for
engaging the drogue 12. Such maneuvering can be achieved using
object recognition software.
In one proposed implementation, collection of information may be
performed using image capture techniques, and object recognition
technologies may be used to identify features (e.g., a pattern of
optical targets or labels attached to the drogue 12 or other
characteristic features of the drogue structure) in the field of
view of the video camera 42. There are a plurality of features in a
captured image that can be extracted to provide a feature
description of the drogue 12. Such feature descriptors for an image
can then be used to identify and locate the drogue 12 in an image.
An object recognition algorithm may be used to extract feature
descriptors and match the extracted features to recognize the
drogue 12. The computer system 62 onboard the receiver aircraft 4
may be configured to continuously calculate the location of probe 8
relative to drogue 12 based on the image data acquired by the video
camera 42 and then control the flight of the receiver aircraft 4 to
continuously reduce the deviation of the location of the probe 8
relative to the drogue 12 from a target relative location
corresponding to full seating of probe 8 inside drogue 12.
FIG. 9 is a diagram identifying some components of an electric
power transfer system onboard the donor aircraft 2 in accordance
with one embodiment. The donor aircraft 2 is equipped with a
computer system 102 that may include one or more computers or
processors, such as a flight control computer, an image processor
and a computer for controlling various mechanical, electro-optical,
electrical and electro-mechanical devices.
In addition, the donor aircraft 2 includes a GPS receiver 104, a
beacon 106, a power supply 94, a power transfer unit 116, a drogue
deployment door 110, and a cable spool 118. Other devices
identified in FIG. 9 are components incorporated in the drogue 12,
including clamps 22, drogue electrical contacts 28, a probe contact
sensor 112, and a drogue electric heater 114. The probe contact
sensor 112 is configured to output an electrical signal when the
electrical contacts of the probe 8 and drogue 12 are in contact, as
previously described. The drogue electric heater 114 may be used to
avoid icing, which could interfere with the electrical connection
via physical contacts. Optionally an electric heater may be
included in the probe 8.
As previously described, the computer system 102 receives GPS data
from a GPS receiver 104 and sends electrical beacon signals to a
beacon 106. The beacon converts the electrical beacon signals into
radio-frequency beacon signals which are broadcast rearwardly from
the tail of the donor aircraft 2.
In the example depicted in FIG. 9, the computer system 102 is
further configured to perform the following operations: (a) send an
activation signal to one of a plurality of actuators 108 to actuate
opening of a drogue deployment door 110 in anticipation of drogue
deployment; (b) send an activation signal to another of the
plurality of actuators 108 to cause a cable spool 118 to unwind the
power cable 10 and thereby deploy the drogue 12; and (c) send an
activation signal to the drogue electric heater 114 for heating the
drogue electrical contacts 28. In addition, the computer system 102
is configured to send an activation signal to yet another of the
plurality of actuators 108 to cause the clamps 22 to engage the
groove 20 in the probe 8 and thereby lock the probe 8 inside the
drogue 12 in response to receipt of the signal from the probe
contact sensor 112 indicating that the probe and drogue electrical
contacts are in a state of electrical connection by contact.
When the probe 8 and drogue 12 are fully engaged and electrically
coupled, the computer system 102 is further configured to output an
activation signal to the power transfer unit 116. In response to
that activation signal, switches in the power transfer unit 116 are
closed, thereby establishing an electrical connection between the
power supply 94 and the drogue electrical contacts 28. The power
supply 94 is then able to provide electric power to the receiver
aircraft 4 for recharging the receiver aircraft's batteries. The
power supply 94 has a power capacity which substantially exceeds
the power needed by onboard systems.
In accordance with alternative embodiments, the battery may be a
battery, a regenerable fuel-cell, a super-capacitor, a
superconducting inductor, or some other device for receiving and
storing electrical energy. The probe may be fixed,
retractable/extendable in flight to reduce drag, or detachable (on
the ground) to reduce drag and weight. Instead of having a
mechanism to deploy/stow a power cable 10 during flight, the power
cable may be fixed or detachable on the ground. The power cable 10
may be attached to or extended from the aft portion of the
fuselage, the empennage, or one or more wing pods of the donor
aircraft 2. Instead of a clamping mechanism, either the probe 8 or
the drogue 12 may be equipped with a suction device to help guide
and hold the probe 8 inside the drogue 12.
In accordance with a further alternative embodiment, the receiver
aircraft 4 is equipped with a hook that may be latched onto a
trapeze bar that depends from the donor aircraft 2. The trapeze bar
and hook include respective sets of electrical contacts that enable
electric power to be transferred from the donor aircraft 2 to the
receiver aircraft 4.
FIG. 11 is a diagram representing a view of a hook and trapeze
mechanism for coupling a receiver aircraft 4 to a donor aircraft 2
during flight in accordance with one alternative embodiment. The
donor aircraft 2 includes a fuselage 3, a truss structure 120
attached to and extending downward from the fuselage 3, and a
trapeze bar 122 attached to (e.g., by fasteners) or joined to
(e.g., by welding) the distal end of the truss structure 120.
Alternatively, the truss structure 120 may be attached to support
structure inside the fuselage 3, such as floor beams.
Still referring to FIG. 11, the receiver aircraft 4 includes a
fuselage 5, a truss structure 124 attached to and extending upward
from the fuselage 5, a guide bar 126 attached to (e.g., by
fasteners) or joined to (e.g., by welding) to the truss structure
124, and a hook 128 integrally formed with the trailing end of the
guide bar 126. The hook 128 is configured to hook onto a central
horizontal section of the trapeze bar 122, as shown in FIG. 11. In
this mechanically coupled state, the trapeze bar 122 and hook 128
are also electrically coupled to enable the transfer of electric
power from the donor aircraft 2 to the receiver aircraft 4.
In the embodiment shown in FIG. 11, the truss structure 124
projects well above the fuselage 5 of the receiver aircraft 4,
while the guide bar 126 also protects the propeller from the
trapeze bar 122 in cases wherein the receiver aircraft 4 is
propeller driven. In alternative embodiments, the hook 128 may be
mounted closer to, or even directly on, the aircraft structure.
With propellers farther from the hook 128 (e.g., twin engines or
pusher), no protective bar is needed. The hook 128 may be on the
bottom or a side rather than on top of the receiver aircraft 4, and
the trapeze bar 122 may be on a top or side rather than a bottom of
the donor aircraft 2. Optionally, the truss structure 120 is
retractable into the interior of the fuselage 3 of the donor
aircraft 2. In alternative embodiments, the truss structure 120 may
be eliminated and the trapeze bar 122 may be mounted directly to
the donor aircraft structure.
FIG. 12 is a diagram representing an end view of a trapeze bar 122
having a hook 128 latched thereon in accordance with one
embodiment. The hook 128 includes an upper guide 136 projecting
from an upper portion 128a of the hook 128 and a lower guide 138
projecting from a lower portion 128b of the hook 128. The upper and
lower guides 136 and 138 guide the hook 128 into lateral alignment
with the trapeze bar 122 as the trapeze bar 122 enters hook
128.
The hook and trapeze mechanism partly depicted in FIG. 12 further
includes a spring-loaded and wedge-shaped pivotable latch 140 (the
spring is not shown) that is rotatably coupled to a pivot axle 142.
The opposing ends of the pivot axle 142 are affixed to a lower
portion of the hook 128. The latch 140 is rotatable between closed
and open positions. The closed position of latch 140 is shown in
FIG. 12. When the trapeze bar 122 enters the hook 128 and passes
the latch 140, the latch 140 closes. The curved edges of the latch
sidewalls hold the trapeze bar 122 between the upper and lower
guides 136 and 138, thereby maintaining electrical coupling between
the electrical contacts on the trapeze bar 122 and the hook 128
during electric power transfer.
As best seen in FIG. 13, the lower portion of the hook 128 has two
mutually parallel slots 150a and 150b formed therein for receiving
respective sidewalls (only sidewall 140a is visible in FIG. 12) of
latch 140 when the latch 140 is pushed by the incoming trapeze bar
122 from the closed position to the open position. The sidewall are
connected to and project in parallel from the side edges of a cross
wall 140b. The cross wall 140b of the latch 140 is formed with a
triangular recess 141 designed to avoid interference of the latch
140 with the lower guide 138 when the latch 140 is opened, e.g.,
when the latch 140 is rotated downward until the cross wall 140b of
the latch 140 contacts the lower portion 128a of hook 128.
Referring again to FIG. 12, the upper guide 136 supports an upper
spring-loaded contact support reed 144, which is a flexible reed
made of electrically insulating material and having a pair of
electrical contacts attached thereto. The lower guide 138 supports
a lower spring-loaded contact support reed 146, which is a flexible
reed made of electrically insulating material and having a pair of
electrical contacts attached thereto. In accordance with an
alternative embodiment, it may be sufficient that only one of the
two contact support reeds is spring-loaded.
FIG. 13 is a top view of the lower portion of the hook 128 and
shows a pair of electrical contacts 148a and 148b disposed on the
lower guide 138. The corresponding pair of electrical contacts on
the upper guide 136 are not shown in the drawings. In accordance
with an alternative embodiment, a single guide may be sufficient,
but using a pair of guides distributes stress better.
As best seen in FIG. 14, the trapeze bar 122 has a central narrow
section 130 having a diameter less than the diameter of the
adjacent sections of the trapeze bar 122 on opposite sides of
central narrow section 130. The central narrow section 130 is
equipped with a pair of electrical contacts 134a and 134b for
transferring power from the donor aircraft 2 to the receiver
aircraft 4 by way of electrical contacts 148a and 148b on the hook
128. In accordance with the proposed implementation partly depicted
in FIGS. 13 and 14, the electrical contacts 148a and 148b (see FIG.
13) incorporated in the hook 128 are made of electrically
conductive material formed into bar-shaped strips, whereas the
electrical contacts 134a and 134b (see FIG. 14) incorporated in the
trapeze bar 122 are made of electrically conductive material formed
into annular bands. When the trapeze bar 122 is disposed inside the
hook 128 as depicted in FIG. 12, the electrical contact 148a on the
hook 128 will be in contact with the electrical contact 134a on the
trapeze bar 122, while the electrical contact 148b on the hook 128
will be in contact with the electrical contact 134b on the trapeze
bar 122.
During an aircraft coupling operation, the receiver aircraft 4
approaches the donor aircraft 2 and pushes the hook 128 onto the
trapeze bar 122. The trapeze bar 122 forces the latch 140 out of
the way and slides into the hook 128 as shown in FIG. 12. During
this motion, the upper and lower guides 136 and 138 (fitting within
the central narrow section 130 of the trapeze bar 122) center the
trapeze bar 122 laterally in the hook 128. More specifically, each
guide has a pair of angled surface which respectively bear against
a pair of conical surfaces 132a, 132b disposed on opposite sides of
the central narrow section 130 of the trapeze bar 122. When the
trapeze bar 122 passes the latch 140, the latch closes, securing
the trapeze bar 122 in the hook 128. Later during the transfer of
electric power, the electrical contacts allow current to flow from
the donor aircraft 2 to the receiver aircraft 4. To release, an
actuator (see latch release actuator 154 in FIG. 15) on the
receiver aircraft 4 retracts the latch 140. The two aircraft can
then separate.
FIG. 15 is a block diagram identifying some components of a system
for releasing the latch 140 that is incorporated in the hook 128
partly depicted in FIGS. 12 and 13. The system includes a latch
release activation device 152 (e.g., a specially programmed
computer or a pilot-operable mechanical input device such as a
lever or button) that outputs an electrical actuator control signal
in response to a determination that the electric power transfer
operation has been completed and the aircraft should disengage. The
system further includes a latch release actuator 154 which may be
activated in response to receipt of an electrical actuator control
signal from the latch release activation device 152. The latch
release actuator 154, when activated, applies a force on the latch
140 that overcomes a spring force being exerted on the latch 140 by
a spring 156, thereby releasing the latch 140. The spring 156 which
is configured to urge the latch 140 to rotate from the open
position to the closed position. The latch release actuator 154
forces the spring-loaded latch 140 to rotate from the closed
position to the open position.
In accordance with the embodiment depicted in FIGS. 11-15, the
donor aircraft 2 includes a fuselage 3, a trapeze bar 122 disposed
outside the fuselage 3, a power supply 94, a power transfer unit
116 configured to transfer electric power from the power supply 94
in a power transfer mode, and electrical conductors (not shown)
electrically coupled to the power transfer unit 116, wherein the
trapeze bar 122 comprises first and second electrical contacts 134a
and 134b which are electrically coupled to the electrical
conductors and disposed on an external surface of a central narrow
section 130 of the trapeze bar 122.
In cases where the receiver aircraft is electrically propelled, the
wired battery charging methodologies disclosed herein extend the
range and duration of flight for receiver aircraft (e.g., unmanned
aerial vehicles). In addition, the technology disclosed herein
reduces the battery size needed to power the electrically propelled
aircraft, thereby reducing cost and increasing flight duration and
efficiency as a result of reduced weight. Furthermore, this
technology enables long-distance missions that are otherwise
difficult for electrically propelled aircraft without a form of
aerial recharging.
While systems and methods for transferring electric power to an
aircraft during flight have been described with reference to
various embodiments, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the teachings herein. In addition, many modifications may be
made to adapt the teachings herein to a particular situation
without departing from the scope thereof. Therefore it is intended
that the claims not be limited to the particular embodiments
disclosed herein.
The embodiments disclosed above use one or more computer systems.
As used in the claims, the term "computer system" comprises a
single processing or computing device (e.g., a computer or a
processor) or multiple processing or computing devices that
communicate via wireline or wireless connections. Such processing
or computing devices typically include one or more of the
following: a processor, a microprocessor, a controller, a central
processing unit, a reduced instruction set computer processor, an
application-specific integrated circuit, a programmable logic
circuit, a field-programmable gated array, a digital signal
processor, and/or any other circuit or processing device capable of
executing the data processing functions described herein.
The method claims set forth hereinafter should not be construed to
require that the steps recited therein be performed in alphabetical
order (any alphabetical ordering in the claims is used solely for
the purpose of referencing previously recited steps) or in the
order in which they are recited unless the claim language
explicitly specifies or states conditions indicating a particular
order in which some or all of those steps are performed. Nor should
the process claims be construed to exclude any portions of two or
more steps being performed concurrently or alternatingly unless the
claim language explicitly states a condition that precludes such an
interpretation.
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